Conventionally, there has been known a DJ controller which is used for acoustic performance by disc jockeys (DJ) as kind of DJ equipment. The DJ controller is used to connect to a computer in which a DJ application is installed, and controls the DJ application by sending operation signals based on user's operations to the computer. While, a structure of a four-deck/four-channel mixer has been commonly used recently as DJ application (for example, see Non-Patent Document 1).
Further, DJ controllers capable of controlling four-deck/four-channel are proposed from each manufacturer with the four decks in such a DJ application. However, if a layout having four-deck/four-channel is adapted in an integral type controller of decks (players) and a mixer, a main frame is oversized. Therefore, each manufacturer uses a structure (layout of two-deck/four-channel) in which only two decks are installed in place of four decks and of which two sides, that is, a front side/a reverse side per each deck can be changed (for example, see Non-Patent Document 2).    [Non-Patent Document 1] Native Instruments Co. “TRAKTOR PRO” http://www.native-instruments.com/#/jp/products/dj/tractor-pro/    [Non-Patent Document 2] Allen & Heath Co. “Xone:DX” http://www.xone.co.uk/dx/